Some are thought to be confused about the risks of cannabis

Officers in the city say during their patrols they have come across children and young teenagers who are using it.

It is a particular concern that children so young are trying the drug because of the impact it could have on their mental development.

Drugs awareness agencies say some are confused about the risks it poses.

Substance risks

Official figures suggest one in 10 13-year-olds have tried the drug, although that does not mean they are regular users.

Drugs awareness agencies such as DrugScope say there is no proven link between mental health problems and smoking cannabis but do point out that the Class C substance can be harmful.

DrugScope said cannabis did not get as much attention as alcohol and heroin, and some young people were confused about the risks it poses.

Devon and Cornwall Police said: "Common misconceptions are that the drug has been legalised and that there are little or no health risks associated with its use.

"It is illegal to grow, produce, supply or possess the drug. Possession of the drug still carries a power of arrest.